This invention relates to an apparatus for testing containers, such as beverage bottles, which will be capped or otherwise closed by a vacuum seal, and for rejecting those containers which do not meet the requirements of a container which can be effectively sealed by a cap or other closure.
This apparatus incorporates the features disclosed and claimed in two of my previous patents, U.S. Pat. Nos. 3,387,704 and 3,496,761, which are hereby incorporated by reference.
U.S. Pat. No. 3,387,704 discloses a machine for gauging the neck diameter of glass bottles moving on a linear conveyor, and for automatically ejecting defective bottles from the conveyor line.
U.S. Pat. No. 3,496,761 discloses a machine for testing the sealing surface of the mouth of glass bottles moving on a linear conveyor, wherein the bottle mouth is covered by a test fixture having a nozzle surrounded by a springpressed sealing diaphragm. A metered volume of air is injected into the bottle through the nozzle, and the retention of pressure in the bottle is sensed by a differential-pressure switch. A defect in the sealing surface is detected by lower than expected pressure resulting from an unacceptably rapid leakage of air past the nozzle diaphragm. This causes the actuation of a switch for ejecting the defective bottle from the conveyor after it has passed beyond the testing area.
The above features disclosed and claimed in both of the above patents were combined into a single bottle testing apparatus. This combination apparatus has been commercially available for some time, and provides the background for understanding the improvement achieved by the present invention.
One of the problems encountered with the sealing surface testing portion of the prior device is that the pressure induced in the bottles from the injection of the measured volume of air varied with atmospheric temperature and pressure. Since the test for detecting an imperfect bottle sealing surface required a comparison by a differential pressure switch, the system was vulnerable to changes in atmospheric conditions. Acceptable bottles might give defective readings, or defective bottles give acceptable readings, unless the differential pressure switch was adjusted for changed atmospheric conditions. Moreover, gradual wear often reduced the volume of air delivered to the bottle, whereby the device would eventually begin rejecting acceptable bottles unless the differential pressure switch was adjusted to compensate for the reduced air volume. Finally, the pressure switch itself was vulnerable to wear and often needed to be replaced.
The improved system of the present invention replaces the differential pressure switch with a linear pressure transducer. The linear output of the pressure transducer is digitized. The digitized output is sent to a microprocessor, which computes a running average of the pressure developed in good bottles, and automatically adjusts the threshold to reject bottles which show finite pressures below a percentage of this running average. The running average thus makes a continuous correction for cylinder wear and atmospheric variations. The initial average pressure developed by the machine when it is first installed is saved in memory and compared at regular intervals to the current running average. If the running average pressure deteriorates below a selected percentage of the initial pressure, indicating excessive wear of the air cylinder, an alarm signal is produced which indicates that maintenance should be performed on the device.
A related advantage gained by the use of the microprocessor is that operating and accounting data can be generated, displayed and stored to give a historical summary of the operating performance of the apparatus and of the number of bottles rejected, the reason for rejection, and the percentages of each.
These and other advantages of the present invention will become apparent upon reading the detailed description of the disclosure which follows.